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WO1997046005A1 - Amelioration du rendu de couleur de recepteurs de television couleur - Google Patents

Amelioration du rendu de couleur de recepteurs de television couleur Download PDF

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Publication number
WO1997046005A1
WO1997046005A1 PCT/IB1997/000317 IB9700317W WO9746005A1 WO 1997046005 A1 WO1997046005 A1 WO 1997046005A1 IB 9700317 W IB9700317 W IB 9700317W WO 9746005 A1 WO9746005 A1 WO 9746005A1
Authority
WO
WIPO (PCT)
Prior art keywords
color
separate
gamma
television receiver
signal
Prior art date
Application number
PCT/IB1997/000317
Other languages
English (en)
Inventor
Matthew S. Brennesholtz
Original Assignee
Philips Electronics N.V.
Philips Norden Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Philips Electronics N.V., Philips Norden Ab filed Critical Philips Electronics N.V.
Publication of WO1997046005A1 publication Critical patent/WO1997046005A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/64—Circuits for processing colour signals
    • H04N9/68—Circuits for processing colour signals for controlling the amplitude of colour signals, e.g. automatic chroma control circuits
    • H04N9/69—Circuits for processing colour signals for controlling the amplitude of colour signals, e.g. automatic chroma control circuits for modifying the colour signals by gamma correction

Definitions

  • the subject invention relates to improving the image on a display of a color television receiver as seen by the viewer by giving more true to life color.
  • CTR cathode ray tube
  • I k*V ⁇ (1)
  • V the CRT drive voltage
  • k the transconductance
  • 7 the gamma value depending on the detailed design of the electron gun in the CRT.
  • ⁇ the value of ⁇ for grid drive CRT's is taken to be 2.2
  • cathode drive CRT's 7 is taken to be 2.8.
  • 7 for each of the three guns in a color CRT is the same.
  • the phosphors are linear with current.
  • type (3) errors studies have shown that consumer actually prefer pictures when there is a positive type (3) error, that is, when 7 RECE ⁇ VER > Y BRO ⁇ DCAST . or 7 RECE ⁇ VER > 2.2. Under these conditions, the colors on the screen tend to be more saturated, i.e., more "vivid".
  • This object is achieved in a method for improving the color rendition of a color television receiver having separate color channels, comprising the steps of generating separate color signals; performing a separate gamma correction on each of the color signals; adjusting a bias setting for each of said gamma corrected color signals; and adjusting a high level drive setting for each of said gamma corrected and bias adjusted signals, wherein said step of performing a separate gamma correction comprises raising each color signal to an exponential power 7 which is adjustable between 0.9 and 1.35 in accordance with the relationship:
  • an apparatus for improving the color rendition of a color television receiver having separate color channel comprising means for generating separate color signals for the respective separate color channels; means for performing a separate gamma correction on each of the color signals; means for adjusting a bias setting for each of said gamma corrected color signals; and means for adjusting a high level drive setting for each of said gamma corrected and bias adjusted signals, wherein said means for performing a separate gamma correction comprises means for raising each color signal to an exponential power 7 which is adjustable between 0.9 and 1.35 in accordance with the relationship:
  • V ' OUT V V IN ⁇ > where 7 is the overall gamma of the camera correction, the gun for each color signal, and the phosphors, whereby said color signals are corrected to eliminate a differential gamma between the separate color channels.
  • a further aspect of the invention provides a color television receiver comprising such an apparatus.
  • Fig. 1 is a block diagram of a known color television receiver
  • Fig. 2 is a block diagram of the color television receiver of Fig. 1 in which the subject invention is incorporated;
  • Fig. 3 is a block diagram of an improvement of the color television of
  • Fig. 4 is a block diagram of a circuit for producing variable 7.
  • Fig. 1 shows a partial block diagram of a color television receiver.
  • a matrix circuit 10 is shown which receives a luminance signal (Y) and color difference signals (R-Y) and (B-Y) from a color demodulator circuit (not shown).
  • a third color difference signal (G-Y) is available which contains no new information, but is a linear combination of the other three signals.
  • the matrix circuit 10 then processes these 3 (or 4) signals to produce R, G and B color signals.
  • a CRT bias circuit 12 then receives these color signals and, in dependence on separate control values, sets the bias for the CRT.
  • this CRT bias circuit allows the adjustment of the black level for the three color signals such that with the particular CRT, a zero drive voltage produces no light output. The adjustment is effected by the receiver manufacturer.
  • the television receiver includes an input for receiving an adjustable "brightness" control value BC which is applied to first inputs of adders 14, 16 and 18 which have second inputs connected to receive three factory cut-off settings R FS , G FS and B FS .
  • the outputs from the adders 14, 16 and 18 are applied to control inputs of the CRT bias circuit 12.
  • the outputs from the CRT bias circuit 12 are applied to separate variable gain amplifiers 20, 22 and 24 having outputs connected to the separate cathodes 34 of the red, green and blue guns in CRT 32.
  • the variable gain amplifiers 20, 22 and 24 are used to control the maximum luminance for each color on display. In order to set this value, the variable gain amplifiers 20, 22 and 24 have gain control inputs to which the receiver manufacturer applies separate correction values to adjust the maximum luminance for each color.
  • provisions are made for user control of the resultant contrast. This is effected by adders 26, 28 and 30 having first inputs interconnected and connected to receive a user control value UGS. Second inputs of the adders 26, 28 and 30 are connected to receive factory adjusted drive setting values R FDS , G FDS and B FDS . Outputs from the adders 26, 28 and 30 are connected to gain control inputs of the variable gain amplifiers 20, 22 and 24.
  • Fig. 2 shows a block diagram of a color television receiver which is similar to the color television receiver shown in Fig. 1, the same blocks carrying the same reference numbers.
  • the variable gamma circuits 36, 38 and 40 include gamma control inputs for receiving a manufacturer-adjusted setting values 7 R , y a and 7 B .
  • the subject invention contemplates using the adders 14, 16 and 18 couple the overall user control value UC to the factory settings to form the final control values for the gamma control inputs of the variable gamma circuits 36, 38 and 40.
  • Fig. 3 shows a preferred embodiment of the color television receiver of
  • Fig. 2 in which the same blocks have the same reference numbers.
  • the factory cut-off setting of the bias may now be automated.
  • the CRT bias circuit 12 is replaced by separate bias circuits 42, 44 and 46 which receive a feedback control signal from the output of the corresponding variable gain amplifier 20, 22 and 24. As such, the bias is automatically set for the correct black level conditions.
  • Fig. 4 shows a block diagram of a variable gamma circuit for use in color television receivers of Figs. 2 and 3.
  • the variable gamma circuit has a log amplifier 50 for receiving the color signal (R, G or B).
  • a variable gain amplifier 52 has an input connected to the output of the log amplifier and a control input for receiving the gamma control value.
  • an anti-log amplifier 54 has an input connected to an output of the variable gain amplifier 52 and an output for supplying the gamma corrected color signal. While each of these components are separately available, it has been found that in order for the log and anti-log amplifiers to co-operate properly, they must be maintained at the same temperature. Hence, the log and anti-log amplifiers should be formed on a same integrated circuit chip. To that end, it would be convenient to form the variable gain amplifier on the same chip. As a further convenience and to enhance economy, all of the variable gamma circuits 36, 38 and 40 may be formed on the same integrated circuit chip.

Landscapes

  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Processing Of Color Television Signals (AREA)

Abstract

Procédé et dispositif servant à améliorer le rendu de couleur d'un récepteur de télévision couleur et consistant en des circuits gamma variables permettant de corriger de façon exponentielle les signaux individuels de couleur. Une commande supplémentaire d'utilisateur permet à l'utilisateur de commander la totalité de la plage gamma du téléviseur, ce qui augmente la saturation des couleurs. L'apport de cette commande gamma d'utilisateur permet d'éliminer la commande séparée de brillance exerçant un effet sur la polarisation générale du tube cathodique.
PCT/IB1997/000317 1996-05-28 1997-03-27 Amelioration du rendu de couleur de recepteurs de television couleur WO1997046005A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US08/653,961 1996-05-28
US08/653,961 US5889565A (en) 1996-05-28 1996-05-28 Method and apparatus for improving the color rendition of color television receivers

Publications (1)

Publication Number Publication Date
WO1997046005A1 true WO1997046005A1 (fr) 1997-12-04

Family

ID=24622977

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB1997/000317 WO1997046005A1 (fr) 1996-05-28 1997-03-27 Amelioration du rendu de couleur de recepteurs de television couleur

Country Status (2)

Country Link
US (1) US5889565A (fr)
WO (1) WO1997046005A1 (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7191402B2 (en) * 2001-05-10 2007-03-13 Samsung Electronics Co., Ltd. Method and apparatus for adjusting contrast and sharpness for regions in a display device
WO2004028133A2 (fr) * 2002-09-21 2004-04-01 Randy Burnworth Procede et appareil, systeme et module pour ameliorer la video
CN1726524A (zh) * 2002-12-13 2006-01-25 皇家飞利浦电子股份有限公司 用于矩阵显示器的自动伽马校正
US7042523B2 (en) * 2003-06-30 2006-05-09 Texas Instruments Incorporated Video correction system and method using logarithmic conversion

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4547797A (en) * 1982-10-12 1985-10-15 Sperry Corporation Apparatus for color tracking and brightness correction for multi-gun color cathode ray tube display
EP0427564A2 (fr) * 1989-11-10 1991-05-15 RCA Thomson Licensing Corporation Traitement de signal vidéo
US5089810A (en) * 1990-04-09 1992-02-18 Computer Accessories Corporation Stacked display panel construction and method of making same
EP0479213A2 (fr) * 1990-10-02 1992-04-08 Ikegami Tsushinki Co., Ltd. Méthode et dispositif de traitement non-linéaire

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL7009523A (fr) * 1970-06-27 1971-12-29
JPS58130676A (ja) * 1982-01-29 1983-08-04 Toshiba Corp ガンマ補正回路
US4589022A (en) * 1983-11-28 1986-05-13 General Electric Company Brightness control system for CRT video display
GB8925438D0 (en) * 1989-11-10 1989-12-28 Rca Licensing Corp Non-linear rgb video signal processing
NL9100174A (nl) * 1991-02-01 1992-09-01 Philips Nv Kleurenbeeld-weergeefinrichting en kleurencamera.
US5398076A (en) * 1993-12-16 1995-03-14 Ati Technologies, Inc. Gamma correcting processing of video signals

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4547797A (en) * 1982-10-12 1985-10-15 Sperry Corporation Apparatus for color tracking and brightness correction for multi-gun color cathode ray tube display
EP0427564A2 (fr) * 1989-11-10 1991-05-15 RCA Thomson Licensing Corporation Traitement de signal vidéo
US5089810A (en) * 1990-04-09 1992-02-18 Computer Accessories Corporation Stacked display panel construction and method of making same
EP0479213A2 (fr) * 1990-10-02 1992-04-08 Ikegami Tsushinki Co., Ltd. Méthode et dispositif de traitement non-linéaire

Also Published As

Publication number Publication date
US5889565A (en) 1999-03-30

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